A large liquid impregnated electrical capacitor comprises a casing which may have a volume of one or more cubic feet and contains a number of capacitor roll sections submerged in an impregnant dielectric liquid. Ordinarily the impregnant liquid in the sealed capacitor may be introduced under a pressure of as much as 10 to 15 pounds per square inch. In order to fill the capacitor casing with the liquid impregnant, it has been a common practice to fill each casing individually by filling the casing through a metal fill tube arrangement which at the termination of the filing process is pinched off and sealed by welding or soldering. The final capacitor, therefore, includes an appendange or short tube section projecting from the casing. Such a projection is undesirable for a number of reasons including the fact that it is exposed to mishandling or other injurious conditions which could cause leakage of the impregnant from the capacitor. At the same time, if the capacitor needs to be repaired in such a manner as to require opening of the capacitor, the seal must be broken and the filling process again performed through the fill tube. In many instances, the pinching and sealing or welding arrangement for the fill tube may not be readily available.
An improved device for filling and sealing a capacitor casing is disclosed in U.S. Pat. No. 3,918,474. Supancic, Jr. which includes a fill tube and a threaded plug seal device. The seal means has a short sleeve with fill holes in its walls and a threaded plug seal therein covering the fill holes. The sleeve is permanently mounted in a wall of a casing to project into the casing. A fill tube is threaded into the sleeve and initially engages the plug seal to move the plug further into the sleeve and away from the fill holes while at the same time sealing itself to the casing. After filling the casing through the sleeve and fill holes, the fill tube is threaded out of the sleeve thus moving the plug seal over the fill holes and against a seal in the sleeve before the fill tube itself is unsealed from the casing. An advantage of this device is that it provides a self-sealing and removable fill tube combination which is adapted for reuse. However, a disadvantage is that the plug seal requires special machined parts and the opening or closing of the seal is by means of a threaded plug seal.
Quite surprisingly, I have discovered an improved capacitor filling and sealing device which is self-sealing and is adapted for reuse, but requires no special machining and eliminates the use of a special plug seal.